Heat exchanger

Abstract

A heat exchanger includes a plate member having several continuously folded plates defining a first opening for reception of a fluid from a first direction and a second opening for reception of another fluid from a second direction, and a frame body enclosing the plate member. The frame body has bottom and top plates, left and right plates, and front and rear plates. Each left and right plate has a height smaller than a width of the folded plate member so that the left and right plate define an upper left hole and a lower left hole in cooperation with the top and bottom plates, and that the right plate defines an upper right hole and a lower right hole in cooperation with the top and bottom plates. Two gasket sheets are disposed on inner surfaces of the top and bottom plates in order to abut hermetically against top and bottom edges of the continuously folded plates.

Description

FIELD OF THE INVENTION

The present invention relates to a heat exchanger, more particularly a plate-type heat exchanger including a folded plate member which serves as heat exchanging medium and which is composed of a plurality of continuously folded plates that can be manufactured at a relatively low cost and its maintenance is easy to conduct, thereby avoiding the problems encountered during use of conventional plate/frame-type heat exchanger.

BACKGROUND OF THE INVENTION

Heat exchangers and its applications are well known in the art. The heat exchanging principle is very easy to understand, i.e. in case first and second fluids are disposed within a receptacle, the fluids tend to exchange heat between each other. Though, the heat exchanging principle is simple, its applications reaches various fields. For instance, the heat exchanging is widely utilized in nuclear power plants, petroleum processing plant, chemical plant, paper production mill, air conditioner, seawater desalination plant, and many others. Heat exchangers are applied in heating, cooling, vaporizing, condensing, energy recycling plant and so forth.

Fundamentally, there are two main types of heat exchangers, namely: (1) tube/shell-type heat exchanger and (2) plate/frame-type heat exchanger. FIG. 1A shows a conventional tube/shell-type heat exchanger 90 and includes a shell body 120 enclosing an upper plate 100 formed with a plurality of coupling holes, a lower plate 110 formed with a plurality of coupling holes, and a plurality small tubes 105 extending into the coupling holes in the upper and lower plates 100,110. The shell body 120 has an upper inlet (102I) formed between the upper plate 100 and the left side wall of the body 120 and via which a first fluid is injected into a first space defined between the upper plate 100 and the left side wall of the body 120, and a lower outlet (102O) formed between the right side wall of the shell body 120 and the lower plate 110 and via which the first fluid flows out. The shell body 120 further has a lower inlet (106I) formed between the upper and lower plates 100, 110 via which a second fluid is injected, and an upper outlet (106O) formed between the upper and lower plates 100, 110 via which the second fluid flows out from the shell body 120.

In the aforesaid heat exchanger 90, the surfaces of the small tubes 105 enable the majority of the heat exchanging operation between the first and second fluids.

Note that in the aforesaid heat exchanger 90, the small tubes 105 are located too densely such that it is relatively complicated, high cost, and difficult to weld the small tubes 105 so as to be integrally from with the peripheries confining the coupling holes in the upper and lower plates 100, 110. In the event, a great number of gasket rings or sheets are utilized instead of the welding process, a considerable manual labor and cost is still required for hermetically sealing the peripheries confining the mounting holes in the upper and lower plates 100, 110. Some stuffing substance, such as resin, can be squeezed into the clearances formed among the small tubes 150 and the peripheries of the mounting holes in the upper and lower plates 100, 110 in order to provide leak-proof effect. In case, the periphery weld or sealing of the coupling hole in the upper or lower plate is leaking or damaged, aging of the gasket rings or sheets due to long term use, it is not easy or possible to trouble shoot the problems. It is also relatively difficult to clean the space located between the small tubes 105.

FIG. 1B illustrates a conventional plate/frame-type heat exchanger 150, which includes a plurality of flat exchange plates 155 and a frame body (not shown). Each heat exchange plate 155 is formed with two upper holes 156A, 156B at an upper section and two lower holes 157A, 157B at a lower section. Several gaskets, in the form of a ring, are provided around the holes in the heat exchange plate 155 in order to provide the leak-proof effect. In the same manner, several gasket sheets 160 are provided at the outer periphery of the heat exchange plate 155 in order to provide the leak-proof effect. Since each gasket has a predetermined thickness, after assembly by pressing, housing space 161, 162, 163 is defined between adjacent two of the heat exchange plates 155.

Though no welding process is required when manufacturing the aforesaid conventional plate/frame-type heat exchanger 150, the manufacture cost is still high because the gaskets 160 are laid adhesively and manually one after another. After assembly and after a period of time, in case of leaking or aging of the gaskets, it is relatively difficult and possible to conduct the essential maintenance of the aforesaid heat exchanger, since all the gaskets 160 are located in the inner portion.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a heat exchanger that can be manufactured at a low cost and that can be maintained with ease.

In accordance with the present invention, the first embodiment of a heat exchanger is provided and includes a folded plate member with a predetermined length and width, a frame body and two gasket sheets. The folded plate member includes a plurality of continuously folded plates defining a first opening for reception of a first fluid from a first direction and a second opening for reception of a second fluid from a second direction opposite to the first direction. The frame body encloses the folded plate member therein, and includes a bottom plate, a top plate, left and right plates, and front and rear plates, wherein each of the left and right plates has a height smaller than the width of the folded plate member so that the left plate defines an upper left hole and a lower left hole in cooperation with the top and bottom plates, and that the right plate defines an upper right hole and a lower right hole in cooperation with the top and bottom plates. The gasket sheets are disposed on inner surfaces of the top and bottom plates in order to abut hermetically against top and bottom edges of the continuously folded plates. In addition, a spacer is disposed between an adjacent pair of the continuously folded plates in order to prevention variation of a clearance defined between two adjacent folded plates due to pressure difference between the first and second fluids.

In accordance with the present invention, the second embodiment of the heat exchanger is provided to have the structure similar to the first embodiment. The only difference resides in that the continuously folded plates have a plain surface including a predetermined regions respectively aligned with the upper and lower left holes in the left plate, and the upper and lower right holes in the right plate, and remaining regions which are offset to the holes in the left and right plates and are dented or pressed with a predetermined pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1A shows a schematic view of a conventional tube/shell-type heat exchanger;

FIG. 1B shows an exploded view of a conventional plate/frame-type heat exchanger;

FIG. 2A is a top view of the first embodiment of a heat exchanger of the present invention with the top plate removed in order to illustrate an interior thereof;

FIG. 2B is a cross-section view of the first embodiment of the heat exchanger of the present invention taken along line P-P′ in FIG. 2A shown together with top and bottom plates;

FIG. 2C is across-section view of the first embodiment of the heat exchanger of the present invention taken along line Q-Q′ in FIG. 2A shown together with top and bottom plates;

FIG. 2D is a cross-section view of the first embodiment of the heat exchanger of the present invention with the top plate removed in order to illustrate an interior thereof;

FIG. 3A illustrates a stretch-out view of an elongated flat plate prior to forming the folded plate member of the second embodiment of the heat exchanger of the present invention; and

FIG. 3B is a cross-section view of the continuously folded plates cooperatively forming the folded plate member employed in the second embodiment of the heat exchanger of the present invention;

FIG. 3C illustrates an another stretch-out view of an elongated flat plate prior to forming the folded plate member of the second embodiment of the heat exchanger of the present invention; and

FIG. 3D is a cross-section view of the continuously folded plates cooperatively forming the folded plate member employed in the second embodiment of the heat exchanger of the present invention.

FIGS. 4A to 4C are top view of the heat exchanger without the top plate according to the present invention.

FIG. 4D is a cross-section view taken along line P-P′ in FIG. 4A shown together with top and bottom plates according to the present invention.

FIG. 4E is a cross-section view taken along line Q-Q′ in FIG. 4A shown together with top and bottom plates according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The heat exchanger provided according to the present invention can be manufactured at a relatively low cost in addition to easy maintenance thereof.

FIG. 2A illustrates a top view of the first embodiment of a heat exchanger of the present invention with the top plate removed in order to illustrate an interior thereof. The heat exchanger includes a heat exchanging folded plate member 5 with a predetermined length and width, a frame body and two gasket sheets 15. The plate member 5 in fact is an elongated metal or heat conductive plate having a thickness between about 0.1 mm to 2 mm, a width W between about 30 cm to 5 meter, and a relatively longitudinal length according to the required folded numbers. The aforesaid elongated metal plate is bent continuously utilizing mechanical processes so as to obtain a plurality of continuously folded plates 5M and a plurality of joint portions 5L, 5R, each of which interconnects two adjacent folded plates 5M. The frame body includes a bottom plate 8B, a top plate 8A, left and right plates 6A, 6B, and front and rear plates 7A, 7B which cooperatively encloses the continuously folded plates 5M in such a manner that the latter define a plurality of first openings OL for reception of a first fluid from a first direction and a plurality of second openings OR for reception of a second fluid from a second direction opposite to the first direction. Note that two adjacent folded plates 5M are spaced apart from each other by a gap ranging from 2 mm to 20 mm.

FIG. 2B is a cross-section view of the first embodiment of the heat exchanger of the present invention taken along line P-P′ in FIG. 2A shown together with the top and bottom plates 8A, 8B. FIG. 2C is a cross-section view of the first embodiment of the heat exchanger of the present invention taken along line Q-Q′ in FIG. 2A shown together with top and bottom plates 8A, 8B. As illustrated, each of the left and right plates 6A, 6B has a height (H) smaller than the width W of the folded plate member 5 so that the left plate 6A defines an upper left hole 12UL and a lower left hole 12DL in cooperation with the top and bottom plates, and that the right plate 6B defines an upper right hole 12UR and a lower right hole 12DR in cooperation with the top and bottom plates 8A, 8B. Note that the upper right hole 12UR and a lower right hole 12DR in the right plate 6B are shielded by the joint portions 5R interconnecting the folded plates 5M (see FIG. 2B). In the same manner the upper left hole 12UL and a lower left hole 12DL in the left plate 6A are shielded by the joint portions 5L interconnecting the folded plates 5M (see FIG. 2C).

Note that each of the upper left and right holes 12UL, 12UR has a height (Hu) greater than the height (Hd) defined by the lower left and right holes 12DL, 12DR. The purpose of designing the height (Hu) of the upper left and right holes 12UL, 12UR greater than the height (Hd) defined by the lower left and right holes 12DL, 12DR is to facilitate smooth flow of the first and second fluids. For instance, the upper left and right holes 12UL, 12UR in the left and right plates 6A, 6B permit smooth outflow of a vapor-type fluid while the lower left and right holes 12DL, 12DR in the left and right plates 6A, 6B permits smooth outflow of a condensate fluid. Of course, the vapor fluid and the condensate or liquid fluid may have different volume. In case, the aforesaid first and second fluids are both liquid or vapor (gas), the height (Hu) of the upper left and right holes 12UL, 12UR and the height (Hd) of the lower left and right holes 12DL, 12DR can be designed to have the same measurement.

The shape of each of the joint portions 5L, 5R should not be flat, but is rather curved. The curvature of the surface of each joint portion 5L, 5R should not be limited. Preferably, the joint portions 5L, 5R (or left and right edges) of the continuously folded plates 5M are in contact with the inner surface of the left and right plates 6A, 6B.

The gasket sheets 15 are disposed on inner surfaces of the top and bottom plates 8A,8B in order to abut hermetically against top and bottom edges of the continuously folded plates 5M in such a manner that the top and bottom edges of the continuously folded plates 5M extend partially into the gasket sheets 15. Each of the gasket sheets 15 has a thickness between about 10 mm to 100 mm, and is made from an elastomeric material. The elastomeric material is selected from a material group including rubber and silica gel.

FIG. 2D is a cross-section view of the first embodiment of the heat exchanger of the present invention with the top plate removed in order to illustrate an interior thereof. As illustrated, the first embodiment further includes a spacer 20L, 20R disposed between an adjacent pair of the continuously folded plates 5 M in order to prevention variation of a clearance “d” defined between the adjacent folded plate 5M due to pressure difference between the first and second fluids. The spacer 20L, 20R includes a plurality of long and short strips 20A, 20B connected to one another in criss-cross manner. Preferably, the spacer 20L, 20R has a web-like configuration. Each long strip 20A is connected transversely to several short strips 20B, and has one end connected to the plates 6A, 6B, as shown in FIG. 2D, or not (not shown).

During the assembly, each spacer 20L is inserted into the respective first openings OL of the continuously folded plates 5M. In the same manner, each spacer 20R is inserted into the respective second openings OR of the continuously folded plates 5M. In other words, the long strip 20A between two adjacent folded plates 5M has one end connected to the left and right plates 6A, 6B, respectively. Alternately, the spacers 20L and 20R are just disposed into the openings OL and OR without connected to the left plate 6A and the right plate 6B. Optionally, to make uniform distribution of the injected fluid, the cross-section of each of the long strip 20A is gradually tapered to the free end with respect to the fixed end. The front plate 7A is mounted to the front ends of the left and right plates 6A, 6B. Afterward, the rear plate 7B is mounted to the rear ends of the left and right plate 6A, 6B so as to define a casing having bottom and top openings. The material for forming the long and short strips 20A, 20B can be selected from a metal group and non-metal materials, or a combination of any one of the metals and the non-metal materials.

After the aforementioned process, one gasket sheet 15 is disposed on the inner surface of the bottom plate 8B. The lower edges of the continuously folded plates 5M are pressed into the gasket sheet 15 on the bottom plate 8B. The other gasket sheet 15 is disposed on the inner surface of the top plate 8A prior to pressing the gasket sheet 15 onto the top edges of the continuously folded plates 5M.

In the first embodiment, the second fluid with a higher temperature can be injected from the upper right opening 12UR in the right plate 6B (see FIG. 2C) while the first fluid with a lower temperature can be injected from the lower left opening 12DL in the left plate 6A (see FIG. 2B) such that after the heat exchanging operation, the fluids will flow out via the lower right openings 12DR in the right plate 6B. In the same manner, the first fluid with a lower temperature can be injected from the lower left opening 12DL in the left plate 6A such that after the heat exchanging operation, the first fluid has a temperature higher than its initial ones and flows out via the upper left hole 12UL in the left plate 6A. Note that the first and second fluids can be injected into the frame body from along one diagonal direction of the frame body and the same flow out along another diagonal direction of the frame body after the heat exchange operation.

The aforesaid first fluid should not be restricted to any specific type. The second fluid should not be restricted either, i.e. liquid or gas or vapor.

FIG. 3A illustrates a stretch-out view of an elongated plate prior to forming the folded plate member of the second embodiment of the heat exchanger of the present invention. The second embodiment has the structure similar to the first embodiment, except in that the continuously folded plates 5M have a surface area including a predetermined regions respectively aligned with the upper and lower left holes 12UL, 12DL in the left plate 6A, and the upper and lower right holes 12UR, 12DR in the right plate 6B, and a remaining regions which are pressed or dented to form a predetermined pattern 40. Note that for forming the predetermined pattern 40, a steel roller (not shown) with smooth surface is first rolled over (dry rolling process) the surface of the elongated metal plate so as to provide an even surface and the even surface is later again rolled over by another steel roller (not shown) having a plurality parallel ribs of specific pattern such that the remaining regions of the continuously folded plates 5M are dented with the predetermined pattern 40. Alternatively, pressing actions can be conducted onto the remaining regions of the continuously folded plates 5M in order to form the predetermined pattern 40.

The configuration of the predetermined pattern 40 should not be limited to any particular design, but is to encompass various designs.

FIG. 3B is a cross-section view of the continuously folded plates that cooperatively form the folded plate member 5 employed in the second embodiment of the heat exchanger of the present invention. The predetermined pattern 40 is preferably composed of a plurality of parallel trenches 41, each of which extends in a direction transverse inclinedly to the longitudinal length of the folded plate member 5, as best shown in FIG. 3A. Alternatively, each trench 41 may extend in a direction transverse perpendicularly to the longitudinal length of the folded plate member 5, as best shown in FIG. 3C.

In the aforesaid embodiment, due to formation of the trenches 41, each of the folded plates 5M has a plurality of concave portions and a plurality of convex portions respectively between two adjacent concave portions. Under this condition, in case two adjacent folded plates 5M are folded, as best illustrated in FIG. 3B, in such a manner to abut against each other, the convex portions of the two adjacent folded plates 5M contact one another while the concave portions thereof cooperatively define a plurality of channels to confine injected fluids flowing along the channels. Note that formation of the trenches 41 (hence the concave portion and convex portions) in the folded plates 5M increases the surface area for contacting with the fluids and increases the heat transfer rate and also increases the uniform distribution of the fluids. Due to the aforementioned facts, the heat transfer ability of the heat exchanger of the present invention is tremendously enhanced.

FIG. 3D is another cross-section view of the continuously folded plates cooperatively forming the folded plate member employed in the second embodiment of the heat exchanger of the present invention shown in FIG. 3C. The only difference resides in that the concave and convex portions of the adjacent two folded plates 5M do not contact each other but with one spacer 15 in each adjacent pair of continuously folded plates to form channels.

Referring to FIGS. 3A and 3C again, the continuously folded plates 5M further have a transition region (shown by x-x′/y-y′ lines) between the predetermined region and the remaining region. The surface area in the transition region of the folded plates 5M should preferably be formed with an inclined slope that gradually inclines from the predetermined region to the remaining region.

According to another preferred embodiment of the present invention, the heat exchanger is composed of the continuously folded plates 5M, two gasket sheets 15, a top plate 8A, a bottom plate 8B, a front plate 7A and a rear plate 7B, as is shown in FIGS. 4A to 4E. The first one of the gasket sheets 15 is disposed between the top plate 8A and the upper edges of the continuously folded plates 5M, and the second one 15 is disposed between the bottom plate 8B and the bottom edges of the continuously folded plates 5M as aforementioned.

FIGS. 4A to 4C are top view of the heat exchanger without the top plate 8A. FIG. 4A shows the continuously folded plates are formed of plain surfaces and openings OL, OR inserted with spacers. FIG. 4B shows the continuously folded plates without spacers. The continuously folded plates have concave and convex pattern formed in such a manner that the convex portions of the two adjacent plates 5M are contact while the concave portions thereof cooperatively define a plurality of channels. FIG. 4C shows the continuously folded plates with concave and convex pattern and spacers. Each spacer is disposed into each adjacent pair of the continuously folded plates 5M.

FIG. 4D is a cross-section view taken along line P-P′ in FIG. 4A shown together with top and bottom plates.

FIG. 4E is a cross-section view taken along line Q-Q′ in FIG. 4A shown together with top and bottom plates.

The operations of the heat exchanger are implemented by flowing in and out through the first openings OL with a first fluid and through the second openings OR with a second fluid.

The following advantages are achieved when the heat exchanger of the present invention is utilized.

(i) When compared to the conventional tube/shell-type heat exchanger, no welding process is required for sealing and connecting the tubes to the top and bottom plates, thereby tremendously lowering the manufacturing and maintenance expense.

(ii) When compared to the conventional plate/frame-type heat exchanger, the gasket sheets are only provided at the top and bottom plates of the shell body. Under this condition, in case the gasket sheets are damaged due to long-term use, fatigue or leakage, replacement thereof can be conducted by simply removing the top and bottom plates with respect to the frame body. Therefore, the maintenance fee is tremendously low. In contrast, since all the gasket sheets or rings are mounted interior of the conventional plate/frame heat exchanger, it is not easy or possible to check and maintenance the condition of the plate/frame heat exchanger. In addition,

The heat exchanger of the present invention is cleared from the disadvantages the aforementioned items (I) and (II). This invention can tremendously reduce the manufacturing and maintenance expense and problem.

As is understood by a person skilled in the art, the foregoing preferred embodiment of the present invention is an illustration of the present invention rather than limiting thereon. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.

Claims

1. A heat exchanger comprising:

a folded plate member with a predetermined length and width, including a plurality of continuously folded plates defining a first opening for reception of a first fluid from a first direction and a second opening for reception of a second fluid from a second direction opposite to said first direction;

a frame body enclosing said folded plate member therein, and including a bottom plate, a top plate, and left and right plates, wherein each of said left and right plates has a height smaller than said width of said folded plate member so that said left plate defines an upper left hole and a lower left hole in cooperation with said top and bottom plates, and that said right plate defines an upper right hole and a lower right hole in cooperation with said top and bottom plates; and

two gasket sheets disposed on inner surfaces of said top and bottom plates in order to abut hermetically against top and bottom edges of said continuously folded plates.

2. The heat exchanger according to claim 1, wherein said frame body further includes front and rear plates connected to said bottom plate, said top plate, and said left and right plates.

3. The heat exchanger according to claim 1, wherein said folded plate member is made from a heat conductive material, and has a thickness between about 0.1 mm to 2 mm.

4. The heat exchanger according to claim 3, wherein said heat conductive material is selected from a metal group including steel, brass, zinc, chromium, aluminum, alloy and titanium.

5. The heat exchanger according to claim 1, wherein each of said gasket sheets is made from an elastomeric material.

6. The heat exchanger according to claim 5, wherein each of said elastomeric material is selected from a material group including rubber and silica gel.

7. The heat exchanger according to claim 1, wherein inner surfaces of said left and right plates are in contact with left and right edges of said continuously folded plates.

8. The heat exchanger according to claim 1, wherein each of said continuously folded plates has a flat surface.

9. The heat exchanger according to claim 1, further comprising a plurality of spacers, each disposed between an adjacent pair of said continuously folded plates in order to prevention variation of a clearance defined between said adjacent pair of folded plates due to pressure difference between said first and second fluids.

10. The heat exchanger according to claim 9, wherein said spacer includes long and short strips connected to each other.

11. The heat exchanger according to claim 9, wherein said spacer has a web-like configuration.

12. The heat exchanger according to claim 1, wherein said continuously folded plates have a surface area including a predetermined regions respectively aligned with said upper and lower left holes in said left plate and said upper and lower right holes in said right plate, and a remaining regions which are pressed or dented with a predetermined pattern.

13. The heat exchanger according to claim 12, wherein said predetermined pattern is composed of a plurality of trenches and wherein each of said continuously folded plates has a plurality of concave portions and a plurality of convex portions respectively between two adjacent concave portions due to formation of said trenches.

14. A heat exchanger comprising:

a folded plate member with a width, including a plurality of continuously folded plates defining a first opening for reception of a first fluid from a first direction and a second opening for reception of a second fluid from a second direction opposite to said first direction;

a frame body enclosing said folded plate member therein, and including a bottom plate, a top plate, a rear plate, a front plate, a left plate and a right plate, said left and right plates in tight abutment with left and right edges of said folded plates, respectively, wherein each of said left and right plates has a height smaller than said width of said folded plate member so that said left plate defines an upper left hole and a lower left hole in cooperation with said top and bottom plates, and that said right plate defines an upper right hole and a lower right hole in cooperation with said top and bottom plates;

a plurality of spacers, each disposed between an adjacent pair of said continuously folded plates in order to prevention variation of a clearance defined between said adjacent pair folded plates due to pressure difference between said first and second fluids; and

two gasket sheets disposed on inner surfaces of said top and bottom plates in order to abut hermetically against top and bottom edges of said continuously folded plates.

15. A heat exchanger comprising:

a folded plate member with a width, including a plurality of continuously folded plates defining a first opening for reception of a first fluid from a first direction and a second opening for reception of a second fluid from a second direction opposite to said first direction;

a frame body enclosing said folded plate member therein, and including a bottom plate, a top plate, and left and right plates, wherein each of said left and right plates has a height smaller than said width of said folded plate member so that said left plate defines an upper left hole and a lower left hole in cooperation with said top and bottom plates, and that said right plate defines an upper right hole and a lower right hole in cooperation with said top and bottom plates, wherein, said continuously folded plates cooperatively have a surface area including a predetermined regions respectively aligned with said upper and lower left holes in said left plate, and said upper and lower right holes in said right plate, and remaining regions which are pressed or dented in such a manner to form a predetermined pattern; and

two gasket sheets disposed on inner surfaces of said top and bottom plates in order to abut hermetically against top and bottom edges of said continuously folded plates.

16. The heat exchanger according to claim 15, wherein said frame body further includes front and rear plates connected to said bottom plate, said top plate, and said left and right plates.

17. A heat exchanger comprising:

a folded plate member formed of a plurality of continuously folded plates defining a first opening for reception of a first fluid from a first direction and a second opening for reception of a second fluid from a second direction opposite to said first direction;

a frame body including a bottom plate, a top plate, a front plate and a rear plate; and

two gasket sheets disposed on inner surfaces of said top and bottom plates in order to abut hermetically against top and bottom edges of said continuously folded plates.

18. The heat exchanger according to claim 17, further comprising a plurality of spacers, each disposed between an adjacent pair of said continuously folded plates.

19. The heat exchanger according to claim 17, wherein said continuously folded plates have a concave and convex pattern formed in such a manner that the convex portions of the two adjacent plates are contact while the concave portions thereof cooperatively define a plurality of channels.

20. The heat exchanger according to claim 17, wherein said continuously folded plates have a concave and convex pattern formed and with one spacer disposed in each adjacent pair of said continuously folded plates.